It is understood Murtough rendezvoused with Sesko's agent, Elvis Basanovic, last Wednesday to gauge the possibility of a transfer.
Sesko, 19, scored the winner in Salzburg's friendly victory over Liverpool on Wednesday and Basanovic is attempting to whip up a market for the Slovenia international. Sesko is contracted to Salzburg until 2026.
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United are in the market for at least one attacking addition, preferably two. United approached the 20-year-old Brian Brobbey, who played under manager Erik ten Hag on loan at Ajax last season, but the Dutchman left RB Leipzig for Ajax permanently earlier this month.
Ajax have valued Antony at 80million and their coach Alfred Schreuder has said he expects the Brazilian to stay as the Dutch champions have already sold Sebastian Haller, Ryan Gravenberch and Lisandro Martinez.
Two days after Murtough met Basanovic, Ten Hag stressed United needed “more options” in their squad as they are still short of two priority targets. The club's pursuit of Barcelona midfielder Frenkie de Jong has entered a twelfth week.
“We signed [Christian] Eriksen for the midfield department, so we are really happy with that,” Ten Hag said. “And yes, I am really happy also with our performances of our midfield department and offensive department at this moment.
“But I also know about this season – we talk about it in Bangkok and Melbourne – it's a lot of games, the World Cup, so we need more options where you have a good team, and it's not only about the team, you need a good squad to get the right results at the end of the season.
“So we have to strengthen the squad even more and we are looking around but we also need the right players.
“There is a reason in a number of games you need more options in offence, clear. I think it's vital if you want to get success, the season is really long but we still also have time to fill that in.”
Ten Hag has indicated Jadon Sancho, Marcus Rashford and Anthony Martial are likely to start the Premier League season against Brighton next Sunday, while Cristiano Ronaldo is in contention to be involved in United's friendly with Rayo Vallecano at Old Trafford on Sunday.